1. Field of the Invention
The present invention relates to a single-chip-based electronic appliance, and more particularly, to an electronic appliance which utilizes only a single chip micro-controller, however can use a data bus to read and write data at the same time for increasing a data transmission speed.
2. Description of the Prior Art
A prior art personal computer system commonly uses DMA (Direct Memory Access) to speed up data transmissions between various computer peripherals. Although DMA can effectively increase a data transmission speed, it has to work with a DMA compatible CPU (central processing unit) and peripheral circuits. The specific component requirements make the circuits and the control of the computer system very complicated and expensive. If data between peripheral circuits are transmitted by a traditional CPU incompatible with the DMA, the CPU has to read data one by one from a peripheral circuit, store each of the data in a register, and then write it to another peripheral circuit. Moreover, the read and write of each of the data require a change of data address of an address bus which results in a long data transmission process.
Please refer to FIG. 1. FIG. 1 is a structural diagram of a conventional DMA controller 70 according to the prior art. When a data is transferring from a memory 72 to a memory 74, an address signal indicative of a transfer origin is outputted from a DMA controller 70 to the memory 72 via an address bus 76, and an address signal indicative of a transfer destination is outputted from the DMA controller 70 to the memory 74 via an address bus 78. When a read signal fed to the memory 72 from DMA controller 70 via a signal line 80 becomes active, data stored in the memory 72 are read out onto a data bus 84, and simultaneously, a write signal fed to the memory 74 from the DMA controller 70 via a signal line 82 becomes active. Thus, the data read out onto the data bus 84 are written in the memory 74. In this fashion, the data transfer from the memory 72 to the memory 74 is completed during one cycle.
As described above, the DMA controller 70 can effectively increase a data transmission speed between the memory 72 and memory 74. But there must be a DMA compatible CPU 90 supporting the DMA controller 70 to make it happen. Therefore, it is not possible for any type of the CPU to have a fast data transmission speed by applying the DMA controller 70. For example, many single-chip-based micro-controllers are utilized in electronic appliances or information appliances (IA), such as washing machine, air-conditioner, burglar-proof device, LCD projector, etc. Unlike the processors in the personal computers, the micro-controllers do not perform bulky and sophisticated calculation. Therefore, such electronic or information appliances accommodate only a micro-controller, instead of a processor, so that the cost can be saved and reduced.
Please refer to FIG. 8. FIG. 8 demonstrates the difference between a processor and a micro-controller. A processor is usually utilized in an extensible system, such as personal computer. There is hardly any RAM and ROM accommodated inside the processor, so large-size extra memory is required to help to achieve massive calculation. Without I/O function built inside, outside ICs (amounting to 3xcx9c5 ICs) must be employed even to carry out a simple instruction or to execute I/O functions. A micro-controller is not connected to the memory or I/O devices. All the memory or I/O controls are performed via the bridge ICs or the DMA controller. However, a micro-controller is usually utilized in electronic appliances, such as an air conditioner, or a washing machine, etc. There are built-in RAM and ROM with several K-bytes memory capacities. No or little extra memory is required. With I/O function built inside, the micro-controller is directly connected to the memory or I/O devices. All the memory or I/O controls are performed without extra ICs or the DMA controller.
In comparison with the processor of a personal computer system, the micro-controller is usually utilized in a less complicated system without sophisticated control instructions to be executed. However, there are more and more chances in the system installed with the micro-controller that massive data transfer is carried out. For example, in the projector, a large quantity of images is sent to the output module to be projected onto the wall. Or in modern home appliances, especially those with Internet communication ability, massive data are to be sent to the graphic module for further image demonstration. To achieve these purposes, massive data transfer must be carried out.
However, in a single-chip micro-controller, it does not support DMA capability. Therefore, when a massive data transfer is required, a long data transmission process would also follow, which results in time-consuming and inconvenience.
It is therefore a primary objective of the present invention to provide an electronic or information appliance with only a simple micro-controller, instead of a powerful processor, but still can perform massive data transfer with efficiency, to solve the above mentioned problems.
In a preferred embodiment, the present invention provides a single-chip based electronic appliance comprising:
a data bus for transmitting data;
an input device electrically connected with the data bus for providing data;
an output device electrically connected with the data bus for receiving data, the output device comprising a device enable pin for controlling the on and off status of the output device; and
a micro-controller electrically connected with the data bus for controlling the input device and output device;
an address bus electrically connected with the micro-controller; and
a position decoder electrically connected between the address bus and the device enable pin of the output device; wherein when an address outputted by the micro-controller to the address bus is a predetermined address, the position decoder triggers the output device by using the device enable pin of the output device so that when the micro-controller reads a datum from the input device through the data bus, it writes the datum to the output device through the data bus in one instruction cycle to increase a data transmission speed between the input device and the output device.
It is an advantage of the present invention that the present electronic appliance can use a traditional single-chip mirco-controller to read and write data concurrently between different memories or I/O ports by using a data bus so as to increase a data transmission speed between them.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment which is illustrated in the various figures and drawings.